The Institute of Electrical and Electronics Engineers (IEEE) Provider Backbone Bridge Traffic Engineering defines how to support provisioning systems that explicitly select traffic engineered paths within Provider Backbone Bridge Networks by allowing a network operator to disable unknown destination address forwarding and source address learning. In addition, Provider Backbone Bridge Traffic Engineering extends the operation of Connectivity Fault Management to support provisioned paths.
PBB-TE defines point-to-point and point-to-multipoint service instances. A point-to-point PBB-TE service instance consists of two unidirectional point-to-point basic connectivity units called Ethernet Switched Paths (ESPs), one for each direction. A point-to-multipoint service instance consists of a downstream multicast point-to-multipoint ESP and “n” upstream point-to-point ESPs.
Maintenance Association End Points (MEPs) are used to monitor PBB-TE service instances. A point-to-point PBB-TE service instance is monitored by a pair of MEPs configured on the bridge ports that are connected by the PBB-TE point-to-point service instance. A point-to-multipoint PBB-TE service instance is monitored by “n” plus one MEPs looted on the bridge ports that are connected by the point-to-multipoint PBB-TE service instance. MEPs monitor the associated PBB-TE service instance by exchanging periodic Continuity Check Messages (CCMs) over the PBB-TE service instance.
On receipt of a CCM frame, a B-component of a Backbone Edge Bridge (BEB) relays the frame as a normal service frame to a Customer Backbone Port (CBP), which is the bridge port where the PBB-TE service instances are terminated. The CBP then demultiplexes the frames by a Backbone VLAN Identifier (B-VID). The CBP then recognizes that it is a CCM frame by an Equal OpCode Demultiplexer. The frame is passed on to a PBB-TE specific demultiplexer which checks the Backbone Source MAC Address (B-SA) and separates the CCMs that belong to the monitored PBB-TE service instance and forwards the CCM to the MEP Continuity Check Receiver.
FIG. 1 is a simplified block diagram of B-VID assignment restriction in an existing PBB-TE service instance. The system includes a first ESP 10, a second ESP 12, a first BEB 14, a second BEB 16, and a third BEB 18. FIG. 1 illustrates several shortcomings of the existing system. ESPs 10 and 12 share the same B-SA, but they have a different Backbone Destination MAC Address (B-DA). In general, the allocation of the ESP 3-tuples should allow the independent selection of B-VIDs for the two ESP because the ESP 3-tuples already differ in the B-DA. However, the existing system unnecessarily requires the allocation of different B-VIDs for the two ESPs (i.e., B-VID1≠B-VID2) because the CBP on the BEB 16 cannot distinguish between the CCM frames of the two incoming ESPs due to the common B-SA. This problem may occur when a point-to-multipoint PBB-TE service instance and a parallel point-to-point PBB-TE service instance is provisioned.
The problem with the existing solution is that it restricts the B-VID assignment of ESPs that connect the same two CBPs unnecessarily. In particular, a multicast point-to-multipoint ESP cannot have the same B-VID as a point-to-point ESP from the root to any of the leaves, or two parallel ESPs cannot share a B-VID even if their B-DA differ.